Process of purifying aldehydes

ABSTRACT

1. A PROCESS FOR REMOVING ACIDIC COMPOUNDS FROM AN AQUEOUS SOLUTION OF AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE AND GLYOXAL, WHICH COMPRISES CONTACTING SAID SOLUTION WITH A RESIN HAVING WEAK BASE ANION EXCHANGE PROPERTIES, SAID RESIN BEING A CRSOSLINKED ION EXCHANGE OR ADSORBENT POLYMERIC RESIN MATRIX HAVING A PLURALITY OF FUNCTIONAL GROUPS SELECTED FROM THE ALIPHATIC OR NONHETEROCYCLIC AROMATIC TERTIARY AMINE OXIDE GROUPS AND ALIPHTIC OR NON-HETEROCYCLIC AROMATIC TERTIARY AMINE GROUPS, WHEREIN AT LEAST ABOUT 5% TO 100% OF SAID FUNCTIONAL GROUPS ARE TERTIATY AMINE OXIDE GROUPS, SAID TERTIARY AMINE OXIDE GROUPS HAVING THE FORMULA   MATRIX-N(=O)(-R)-R&#39;&#39;   WHEREIN R AND R&#39;&#39; ARE THE SAME OR DIFFERENT ALKYL, ARYL, ALKARYL, OR ARALKYL GROUPS, OR WHEREIN R AND R&#39;&#39; CAN BE TAKEN TOGETHER TO FORM A SATURATED HETEROCYCLIC RING WITH THE ATTACHED NITROGEN ATOM, OR WHEREIN R AND R&#39;&#39; CAN BE JOINED WITH AN R OR R&#39;&#39; IN ANOTHER TERTIARY AMINE OXIDE OR TERTIARY AMINE GROUP THROUGH AN ALKYLENE OR ALKYLENEAMINO CHAIN, AND WHEREIN SAID TERTIARY AMINE GROUPS HAVE THE FORMULA   MATRIX-N(-R)-R&#39;&#39;   WHEREIN R AND R&#39;&#39; ARE AS DEFINED ABOVE.

United States Patent U.S. Cl. 260-601 R 2 Claims ABSTRACT OF THEDISCLOSURE A process for removing acidic compounds from aqueoussolutions of aldehydes is disclosed utilizing resins containingaliphatic or non-heterocyclic aromatic tertiary amine groups which havebeen converted to the corresponding tertiary amine oxide groups.

This application is a divisional application of copending applicationSer. No. 851,456 filed Aug. 19, 1969 now Pat. No. 3,749,684.

This invention relates to novel resins which are useful as adsorbentsand as weakly basic ion-exchange resins.

When conventional anion exchange resins are converted during use fromtheir basic to their acidic form, they undergo a significant volumechange, or swelling. During regeneration, the resins are changed fromtheir acidic to their basic forms, thus going through the originalvolume change in reverse. After several of these base-tobase cycles, therepeated changes in volume of the ionexchange beads cause them tofragment or crack, leading to a diminishing of their usefulness, and inparticular their ion-exchange and adsorbent usefulness. Therefore, itwould be desirable to have an ion-exchange resin which would be subjectto little or no volume change during use and consequently would showgreater resistance to physical breakdown. In J. Chem. Soc. 1963, 1519,and in Israeli Pat. 144 5/1960, Heller et al., describe N-oxides ofcertain polyvinyl pyridine resins. However, when used as anionexchangers, these polymers showed a large volume change in differentionic for-ms, an acknowledged disadvantage for many operations.

It has now been found that when at least about 5% of the tertiary aminegroups of certain polymeric resins containing tertiary aminefunctionality are converted to the corresponding tertiary amine oxidegroups, there is very little or no volume change during acid and basecycling operations, and that beads of such amine oxide such as amido,nitro, or cyano groups. As described below,-

the percentage of amine oxide groups can easily be varied between about5% and 100%, and that degree of con version to amine oxide functionalitycan be chosen which will give the best results in a specificapplication.

Any aliphatic or non-heterocyclic aromatic tertiary amine group whichcan be converted to a tertiary amine p ICC oxide group will be asuitable substituent from which the resins of the invention can be made.The tertiary amine oxide groups in the resins of the invention willgenerally have the formula i matrix-IlI-R' 0 wherein R and R are thesame or different alkyl, aryl, alkaryl or aralkyl groups, or wherein Rand R can be taken together to form a saturated heterocyclic ring withthe attached nitrogen atom or can be joined with an R or R' group inanother nitrogen-containing functional group through an alkylene oralkylene-amino chain. The tertiary amine groups will generally have theformula matrix-N wherein R and R are as defined above.

Among the groups which R and R can represent are methyl, ethyl, propyl,hexyl, cyclohexyl, dodecyl, phenyl, benzyl, p-methylbenzyl, and thelike. Among the heterocyclic groups which R and R can be taken togetherto form are pyrrolidinyl, piperidino, morpholino, and the like.

A wide variety of polymeric resin matrices is useful. in making thenovel amine oxide-containing resins of the present invention, and anypolymeric resin having tertiary amine functional groups can be used.Such resins include both macroreticular and gel type resins, as well asa wide variety of condensate resins. All of the resins used in makingthe amine oxide-containing resins of the invention are known and areavailable from a number type resins, while the preparation process isvaried toimpart diiferent characteristics, especially different poros-=ity, to the two types of resins. When macroreticular or gel type resinsare used to prepare the resins ofthe invention, the nature of thepolymer which comprises the back-- bone of the resin is unimportant, theonly requirement being that the resin ultimately contain tertiary amine:

groups which can be converted to tertiary amine oxide groups. However,in general, the backbone of these resins will be cross-linked copolymerof (l) a polyunsaturated" monomer, containing a plurality ofnon-conjugated CH =C groups, which acts as a cross-linking agent'an'd(2) a monoethylenically unsaturated monomer.

Suitable polyunsaturated cross-linking agents include divinylbenzene,divinyltoluenes, =divinylnaphthalenes, di-

allyl phthalate, ethylene glycol diacrylate, ethylene glycoldivinylethylbenzene, di-

dimethacrylate, divinylxylene, vinylsulfone, divinylketone,divinylsulfide, allyl acrylate,

diallyl maleate, diallyl fumarate, diallyl succinate,"di'allyl"carbonate, diallyl malonate, diallyl oxalate, diallyl adipate,

diallyl "sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate,triallyl tricarballylate, triallyl aconitate-,-'triallyl citrate,triallyl phosphate, 'N,N'-methylenediacrylamide, N,N-methylenedimethacrylamide, N,N-ethylenediacrylamide, trivinylbenzene,trivinylnaphthalen'e, polyvinylanthracenes and the polyallyl andpolyvinyl ethers of glycol glycerol, pentacrythritol, resorcinol and themonothio or dithio derivatiesof glycols.

. Preferred cross-linking monomers include polyvinyl aromatichydrocarbons, such as divinylbenzene and trivinylbenzene, glycoldimethacrylates, such as ethylene glycol dimethacrylate, and polyvinylethers of polyhydric alcohols, such as divinoxyethane andtrivinoxypropane. The amount of cross-linking agent can be varied widelybut since the total utilizable capacity of the final resin as ananion-exchange resin decreases with an increase in the amount ofcross-linking agent, an amount of about 2% to about 20%, and preferablyabout 3 to 10%, on a molar basis is usually adequate.

\ Suitable monoethylenically unsaturated monomers include esters ofacrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate,isopropyl acrylate, butyl acrylate, tert-butyl acrylate, ethylhcxylacrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate,phenyl acrylate, alkylphenyl acrylate, ethoxymethyl acrylate,ethoxyethyl acrylate, ethoxypropyl acrylate, propoxymethyl acrylate,propoxyethyl acrylate, propoxypropyl acrylate, ethoxyphenyl acrylate,ethoxybenzyl acrylate, ethoxycyclohexyl acrylate, the correspondingesters of methacrylic acid, styrene, o-, mand p-methyl styrenes, andm'-, and p-ethyl styrenes, vinyl naphthalene, vinyltoluene andvinylnaphthalene. A class of monomers of particular interest consists ofstyrene and the esters of acrylic and methacrylic acid with a (l -Caliphatic alcohol.

The polymerization reaction is generally carried out in the presence ofa catalyst. Suitable catalysts which provide free radicals to functionas reaction initiators include benzoyl peroxide, t-butyl hydroperoxide,curnene hydroperoxide, tetralin peroxide, acetyl peroxide, caproylperoxide, t-butyl perbenzoate, t-butyl diperphthalate, methyl ethylketone peroxide.

The amount of peroxide catalyst required is roughly proportional to theconcentration of the mixture of monomers. The usual range is 0.01% to 5%of catalyst with reference to the weight of the monomer mixture. Theoptimum amount of catalyst is determined in large part by the nature ofthe particular monomers selected, including the nature of the impuritieswhich may accompany the monomers.

Another suitable class of free radical generating compounds which can beused as catalysts are the azo catalysts, including for example,azodiisobutyronitrile, azodiisobutyramide, azobis(a,adimethylvaleronitrile), azobis(a-methylbutyronitrile), dimethyl,diethyl, or dibutyl azobis(methylvalerate). These and other similar azocompounds which serve as free radical initiators, contain an -N=N- groupattached to aliphatic carbon atoms, at least one of which is tertiary.An amount of 0.01% to 2% of the weight of monomer or monomers is usuallysufficient.

In making the gel type resins, a wide variety of polymerizationprocesses well known in the art can be used. However, the preferredmethod is emulsion or suspension polymerization in a liquid, such aswater, which is not a solvent for the monomeric material. This methodproduces the polymer directly in the form of small spheroids or beads,the size of which can be regulated and controlled. By adjustments in thecomposition of the suspending medium and in the rate of agitation duringpolymerization, the suspension polymerization process can be made toproduce spheroids or beads of a wide range of elfective particle sizes.

In preparing the macroreticular resins, the polymerization reaction iscarried out in the presence of a precipitant which is a liquid (a) whichacts as a solvent for the monomer mixture and is chemically inert underthe polymerization conditions and (b) which is present in such amountand which exerts so little solvating action on the product cross-linkedcopolymer that phase separation of the product copolymer takes place asevidenced by the fact that the product copolymer is no more thansemitransparent and is preferably opaque when associated with a fluidhaving a ditterent refractive index.

The determination of the most effective precipitant and the amountsrequired for the formation of a particular copolymer may vary from caseto case because of the numerous factors involved. However, althoughthere is no universal or single class of precipitants applicable to allcases, it is not too diflicult to determine which precipitants will beelfective in a given situation. The requirements of solubility with themonomer mixture and low solvating action on the product copolymer can betested empirically and the solubilities of many monomers and copolymersare well known from publications and textbooks.

Cross-linked copolymers are generally insoluble, but, depending upon thedegree of cross-linkage, they can be swollen by liquids which might beconsidered as being good solvents and if the product crosslinkedcopolymer is so solvated by a liquid that it undergoes swelling then theliquid in question is unsuitable as a precipitant.

As a further guide in the selection of a suitable precipitant, referencemay be made to scientific literature, for instance, as discussed inHildebrand and Scott, Solubility of Non-Electrolytes, 3d ed., New York,1950. In general, it may be stated that sufiiciently wide difierences inthe solubility parameters of copolymer and solvent, respectively, mustexist for the precipitant to be effective and that, once an effectiveprecipitant has been located, the behaviour of many other liquids can bepredicted from the relative position of the reference polymer andprecipitant in published tables, within the accuracy of such publishedinformation. Furthermore, if the solubility parameter of a given polymeroccupies an intermediate position in these tables, solvents with bothhigher or lower parameters may become effective.

A minimum concentration of any particular precipitant is required toeffect phase separation. This is comparable to the observation that manyliquid systems containing two or more components are homogenous whensome components are present in only minor amounts; but, if the criticalconcentration is exceeded, separation into more than one liquid phaseWill occur. The minimum concentration of the precipitant in thepolymerizing mixture will have to be in excess of the criticalconcentration. The amounts in excess of such critical concentration canbe varied and they will influence to some extent the properties of theproduct so formed.

Too high a concentration of the precipitant may be undesirable forpractical reasons since the rate of copolymerization may decrease andthe space-time yields become low. In many cases, the amount ofprecipitant employed may be between 25 per cent and 60 per cent of thetotal weight of the monomer mixture and the precipitant.

The amount of precipitant liquid required to effect phase separationvaries inversely with the degree of crosslinking of the copolymer sothat the greater the crosslinker content the lesser is the amount ofprecipitant employed.

As stated above, the chemical character of the precipitant may varyappreciably, depending on the monomer mixture which is used. Whenemploying aromatic hydrocarbon type monomers, such as, for instance,styrene and divinylbenzene, alkanols With a carbon atom content of from4 to 10 will, if suflicient crosslinker is used, elfect the desiredphase separation when used in amounts of from 30% to 50% of the totalweight of monomers and precipitant.

Saturated aliphatic hydrocarbons containing at least 7 carbon atoms,such as heptane and isooctane, may be employed as precipitants foraromatic hydrocarbon systems, such as styrene and divinylbenzene. Theamounts employed can be varied, depending on the degree of crosslinkage,from 30% to 50% of the total weight of the monomers and precipitant.

When employing acrylic esters as the monounsaturated monomers, alkylesters can be efiectively employed as precipitants. Typical estersinclude n-hexyl acetate, 2-ethylhexyl acetate, methyl oleate, dibutylsebacate, dibutyl adipate and dibutyl carbonate. The esters must have acarbon atom content of at least 7. The concentrations required will varysomewhat with the ester being used and with the amount of cross-linkingmonomer but from 30% to 50% based on the combined weight of the monomersand the precipitant will generally cause the desired phase separationand the formation of a macroreticular structure within the polymerizedmass.

Higher aliphatic hydrocarbons containing at least 7 carbon atoms, suchas heptane and isooctane, may be employed as precipitants when employingacrylic esters as the monoethylenically unsaturated monomers. Theamounts employed can be varied from 25% to 50% based on the combinedweight of monomers and precipitant.

Many polymerization methods can be used in preparing thesemacroreticular resins. The preferred method, however, is suspensionpolymerization. In this case, an additional factor must be considered,namely, the solubility, i.e., miscibility, of the precipitant in thesuspending medium. Since suspension polymerization of most ethylenicallyunsaturated monomers is generally conducted in aqueous media, mostfrequently it is the water-solubility of the precipitant which must beconsidered. While precipitants with water-solubilities as high as 20grams per 100 grams of water can be employed, a low water-solubility ispreferred because of handling ease, ease of recovery, and processingeconomies. As is well known, however, it is possible to decrease thewater-solubilities of compounds by adding salts to the aqueous phase andthis method also may be employed to decrease the water-solubilities of aprecipitant liquid. The general position is that, when suspensionpolymerization is used, the precipitant must be either immiscible oronly partially miscible with the suspending medium.

Other suitable methods for preparation of the macro reticular resins aredisclosed in US. Pats. 3,275,548 and 3,357,158.

The process by which the tertiary amine groups are introduced into theresin matrices will vary according to the type of polymer in thebackbone of the resin. For example, when styrene or another aromaticmonovinyl monomer is employed in making the resin backbone,halomethylation of the resin followed by reaction with a secondary aminewill introduce tertiary amine groups into the resin, and when thebackbone is an acrylic or a methacrylic ester, reaction of the resinwith .a compound having both a primary amine group and a tertiary aminegroup will produce a resin with tertiary amine functionality. When aglycidyl ester of acrylic or methacrylic acid is used, the tertiaryamine functionality can be introduced by direct reaction of the resinwith a secondary amine.

The halomethylation reaction involves introducing into the polymer aplurality of bromoalkyl or, preferably, chloroalkyl groups. These groupswill have the general formula C H -X, where n is an integer of 1 to 4.While groups containing one to four carbon atoms can be used, it ispreferred to employ those compounds in which chloromethyl groups, CH Cl,are added to the insoluble p lymer, because the chloromethyl productsare by far the most reactive. The carbon atoms in the group may be in astraight or branched chain.

The step of haloalkylating the insoluble hydrocarbon copolymer may becarried out in a variety of way-s For example, the polymer may bereacted with a mixture of an aldehyde and hydrochloric acid or a mixtureof a dihalide and a Friedel-Crafts cataylst.

The preferred procedure is to treat the particles of polymer withchloromethyl ether and a Fn'edel-Crafts catalyst. During the step ofhalomethylating, some cross-linking of the polymer by thehalomethylating agent can take place.

When the polymer being treated is already cross-linked and iscompletelly insoluble, the particles thereof may be immersed in thechloromethyl ether until they swell, after which the Friedel-C-raftscondensing agent is added. This soaking and swelling of the particles ofpolymer facilitates the chloromethylation reaction within the pores ofthe particles when the Friedel-Crafts catalyst is added.

When the polymer being treated is linear, as in the case of polystyreneper se, or is cross-linked to only a slight extent as, for example, bythe use of about 0.1% of a divinyl cross-linker, the treatment with thehalomethylating agent, particularly chloromethyl ether, results incrosslinking and insolubilization of the polymer as well as inhalomethylation thereof. In such instances methylene bridges link themolecules of polymer together. In the preferred process ofsimultaneously cross-linking and chloromethyla'ting, the chloromethylether and the Friedel- Crafts condensing agent are first mixed and theparticles of aromatic hydrocarbon polymer, such as polystyrene, are thenadded to or treated with this mixture. Linear polymers, such aspolystyrene, soften rapid-1y and dissolve in chloromethyl ether alone;but, when the Friedel-Crafts catalyst is present, the cross-linking andinsolubilization of the polymer occurs so rapidly that the polystyreneparticles are prevented from dissolving or softening and coalescing.Polystyrene, when treated in this fashion, has all the properties of aninsoluble infusible, cross-linked polymer and, in fact, appears to bemore highly cross-linked than a similarly treated poly-styrene polymerwhich had been previously cross-linked with 1% divinyl benzene, but itdoes not appear to be as highly cross-linked as a chlorome'thylatedcopolymer of polystyrene cross-linked with 6% divinyl benzene.

The extent of the halomethylation reaction is conveniently determined bya halogen analysis. It is desirable that as many hal-omethyl groups aspossible be introduced into the insoluble copolymer because the numberof such groups determines the number of polar groups that can beintroduced into the final product; and the number of such polar groupsdetermines the capacity of the resin to adsorb ions.

The next step in the preparation of the tertiary amine containing resinsis the amination of the haloalkylated copolymer with a secondary amine.This reaction is preferably carried out by adding the amine to thehaloalkylated polymer while the latter is suspended and agitated in aliquid which is a solvent for the amine. The mixture may be allowed toreact at room temperature or, preferably,

at elevated temperatures, after which the resin, containing aminogroups, is freed from the liquid.

It has been found to be advantageous to swell the haloalkylated polymerprior to its reaction with the amine. This swelling facilitates thesubsequent amination reaction and may be carried out by soaking thepolymer in a suitable liquid. The most common liquids for this purposeinclude aromatic hydrocarbons such as benzene and toluene. Frequently,the volume of the polymer will increase as much as although the amountof swelling depends to a great extent upon the amount of cross-linkingwhich has taken place during the preparation of the original polymer. Ingeneral, the amount of swelling is inversely proportional to the degreeof cross-linking.

The amines which are employed are used in the form of the free base. Theprime requirement is that they contain at least one amino-nitrogen atomto which is attached one reactive hydrogen atom. The amines which areprefer-red in this application are those in which the amine group orgroups are attached to a hydrocarbon group. Other amines may be used,however, including those wherein the hydrocarbon group of the aminecarries a substituent group. Such amines may be exemplified bydiethanolamine. For best results, the amino compound should not containsubstituent groups which are themselves reactive under the conditionsemployed in aminating the haloalkylated resin.

The hydrocarbon portion of the amine can be alkyl, aryl, cycloalkyl,aralkyl, or a-lkaryl. The following typify the amines which are suitablein this invention when used individually or in mixtures with oneanother: dirnethy'lamine, dibutylamines, dibenzylamine, benzyl aniline,benzyl ethylamine, methyl aniline, dicyclohexyla-mine, anddiethanolamine.

Weak base resins are also prepared by reacting esters with amines toform amide linkages. The reaction will generally be carried out at a pottemperature above 140 C. Temperatures as high as the boiling point ofthe amino compound or up to depolymerization temperaature of thepolyester can be used. While the optimal reaction temperature willdepend on the particular amine which is used, the overall range ofoperable temperatures is usually about 140-250 C.

In a satisfactory procedure a large excess of the liquid amino compoundis employed so that the reaction mixture is fluid at all times and canbe easily stirred. The reaction between the particles of resin and theamino compound progresses more smoothly if it is conducted undersubstantially anhydrous conditions. The chemical reaction involved atthis point is one of aminolysis. Primary amino groups of the polyaminocompounds react with the ester groups of the polyesters and as a resultmolecules of alcohol are liberated. The alcohol vaporizes and isseparated and recovered from the reaction mixture by distillation.Measurement of the amount of liberated alcohol provides a convenientmeans of following the progress of the reaction.

At the end of the reaction the mixture in the reactor is treated withwater. The mixture can be poured into water; but it is much moreadvantageous to add water slowly to the contents of the reactor. Thelatter method is much preferred because it does not cause shattering orspalling of the spheroidal particles of the resinous product. The beadsof resin are then removed from the mixture of water and unreacted amineand are thoroughly washed with water and/ or an alcohol such as methanolor ethanol. The resin is now in a suitable form for use in adsorbinganions from fluids. In commercial production, however, it is recommendedthat particles of resin be given a thorough washing with dilute mineralacid; e.g., hydrochloric acid, in order to convert them into the saltform, followed by a thorough washing with sodium hydroxide in order toregenerate them completely to the form of the free base. The excessamino compound is freed of water and is recovered by distillation.

The amino compounds used to react with the crosslinked esters mustcontain at least two amino groups, at least one of which is a primaryamino group, and one tertiary. The primary amino groups react with theester groups in the crosslinked copolymer to form amido groups. Usefulamino compound include N-aminopropylmorpholine, N aminoethylmorpholine,N aminoethylpiperidine, N-aminoethylpyrrolidine,dimethylaminopropylamine, dimethylaminoethylamine,diethylaminopropylamine, and the like.

Among the condensate resins which are useful in making the amine oxidecontaining resins of the invention are those made by condensing anepihalohydrin, such as epichlorohydrin, with a polyalkylene-polyamine,such as diethylenetriamine, triethylenetetramine,tetraethylenepentamine, iminobispropylamine and the like. One of thevarious useful processes for carrying out the condensation involvespreparing an initial, partial condensate, or precondensate syrup, of anepihalohydrin and an aqueous solution of a polyalkylenepolyamine.Polymerization is permitted to proceed only to the point where asomewhat viscous syrup is produced. The partially condensed, slightlyviscous material is then added, with agitation, to a hot, inert,organic, non-solvent liquid containing a small amount of a surfaceactive agent which tends to prevent or minimize the agglomeration orfusion of the desired globules or spheroidal particles which are formedas a result of rapidly stirring or agitating the mixture. The rate ofagitation is predetermined to produce a desired particle size. Thereaction mixture is heated, with agitation, until solid resin beads areformed as a result of further polymerization. The temperature of themixture is increased to remove as much of the water contained in theprecondensate syrup in the form of an azeotropic mixture with theorganic, non-solvent liquid. Heating is then continued to permit thecomplete polymerization of the resin condensate. The nonsolvent can thenbe drained from the spheroids or beads.

Other methods and variations for making suitable condensate resins aredisclosed in U.S. Pat. 2,898,309 and 3,005,786.

Any other polymeric resin matrix containing aliphatic ornon-heterocyclic aromatic tertiary amine groups which can be convertedto their tertiary amine oxide form can also be used in making the resinsof the invention.

The tertiary amine groups in the various resin matrices are easilyconverted to their respective tertiary amine oxides by reacting themwith aqueous hydrogen peroxide. In general, the degree of conversion,that is, the percentage of tertiary amine groups converted to tertiaryamine oxide groups, can be controlled by varying the reaction time, thereaction temperature, the amount of hydrogen peroxide used, or otherparameters. In general, if complete or almost complete conversion toamine oxide functionality is desired, a reaction time of about 144 hoursat a temperature of about 25 C. to 30 C., using about 3 moles ofhydrogen peroxide for each mole of tertiary amino groups, will generallybe suflicient to effect the conversion. Of course, using a shorterreaction time or a lesser amount of hydrogen peroxide will give a lowerdegree of conversion of tertiary amine groups to tertiary amine oxidegroups.

To determine the degree of conversion to amine oxide functionality, anyof a wide variety of known analytical procedures can be employed. Amongthe physical methods which can be utilized are the determination of theamount of oxygen liberated during the conversion reaction and aninfrared spectral technique in which the ratio of the band attributableto the amine oxide functional group to the band attributable to anotherfunctional group in the resin, such as an aromatic band in astyrene-bacltboned resin, is measured and compared to the same ratio ina amine oxide-converted resin. Among the chemical methods which can beutilized are a two-step acid-base titrimetric procedure, in which afirst titration of both the tertiary amine and tertiary amine oxidegroups is carried out, and after quaternization of the free tertiaryamine groups with methyl iodide, a second titration is carried out. Asecond method involves an iodometric titration, using potassium iodideand sodium thiosulfate, in glacial acetic acid, in which the amine oxidecontent is determined directly. The latter two techniques are describedin Anal. Chem., 34, 1849 (1962) and J. Prakt Chem. (4 Reihe), 19,260-265, respectively. Other appropriate analytical techniques can alsobe used.

All of the resins of the present invention are useful as weakly basicanion-exchange resins. When used as ionexchange resins, the resins ofthe invention show unexpected greatly enhanced physical stability, thatis, resistance to cracking, fragmenting, or other physicaldeterioration, without significant loss in exchange capacity.Furthermore, these resins are also quite useful as adsorbents, andparticularly in removing polar compounds from non-polar compounds. Forexample, the resins of the invention are useful in adsorbing aliphaticalcohols or phenolic compounds from organic solvents. in addition toshowing increased physical stability as adsorbents, the resins of theinvention also have a greater capacity in adsorption applications thancorresponding resins in their tertiary amine form.

The following examples will further illustrate this invention but arenot intended to limit it in any way.

9 EXAMPLE 1 To a one-liter three-neck flask filled with a stirrer,thermometer, and gas outlet tube were added 1.0 moles of amacroreticular, weak base anion-exchange resin containing tertiary aminefunctionality on a styrene-divinylbenzene matrix, 3.0 moles of 30%hydrogen peroxide, and 150 ml. of deionized Water. The system was sealedand the gas liberated was collected by water displacement from aninverted graduated cylinder. The resulting slurry was stirred at roomtemperature for six days. The reaction mixture can be cooled slightlyfor the first hour to maintain a reaction temperature of less than 30C., if desired.

The reaction mixture was then transferred to a graduated cylinder andbackwashed with deionized water until the washings did not liberateiodine from an acidified acetic acid 20% aqueous sodium iodide solution.The resin was filtered and bottled moist.

The resin produced by the above procedure was 100% converted to theamine oxide form, and had the following characteristics:

(Unconverted resin) weak base capacity3.68 meq./ g meq./g 4.02

strong base capacity0.55 meq./g. meq./g 0.21

anion exchange capacity4.23 meq./ g. meq./g 4.23

Solids-34.6% percent 41.4

EXAMPLE 2 Following the procedure of Example 1, 100 g. of a gel type,weakly basic anion exchange resin possessing tertiary aminefunctionality in a crosslinked acrylic matrix, 120 g. of 30% hydrogenperoxide, and 150 ml. of deionized water were stirred at roomtemperature for three days. Cooling was necessary during the initialreaction period and some efiervescence was noted at this time.

After the reaction was complete, the resin was washed and filtered.

The resin produced by the above procedure had the followingcharacteristics:

(Unconverted resin) Anion exchange capacity6.00 meq./ g. ..meq./g 6.13Solids-32.4% percent 43.5

EXAMPLE 3 Following the procedure of Example 1, using the same resin asstarting material, several amine oxide-containing resins were prepared,containing less than 100% conversion of the tertiary amine groups totertiary amine oxide groups. Table I summarizes the characteristics ofthe various resins so prepared.

10 the graduate cylinder. The resin was backwashed to remove any fines.

The resin produced by the above procedure was approximated 25% convertedto the amine oxide form, and

had the following characteristics:

(Unconverted resin) Weak base capacity10.39' meq./g. meq./g 11.11

Strong base capacity0.11 meq./g. meq./g 0.10 Anion exchangecapacity10.50

meq./g. meq./g 11.21 Solids-32.4% percent 33.5

When an excess of hydrogen peroxide is used complete conversion to theamine oxide can be obtained.

EXAMPLE 5 Physical Stability Towards Acid Shock The following procedurewas used to evaluate the stability of various amine oxide-containingresins and their untreated counterparts.

A few hundred beads of a suitable uniform size (usually a 20/30 meshscreen cut) of the resin are placed in a 250 ml. beaker. Approximately200 ml. of aqueous acetic acid are added and the resulting slurry isstirred briefly about every five minutes. After about fifteen minutes ofcontact with the acid, the resin is transferred onto a small 325 meshscreen and thoroughly rinsed with deionized water. The resin is thenreturned to the beaker using as little water as possible (no more thanml.) and approximately 200 ml. of 4% aqueous sodium hydroxide are added.The resin is left in contact with the sodium hydroxide solution forabout 15 minutes with brief stirring every five minutes, and then rinsedwith deionized water as above. The entire acid- 0 base cycle is carriedout four times and, after the final rinsing, the beads are examinedmicroscopically to determine the extent of physical deterioration.

Table II summarizes the stability, as measured by the above procedure,of the amine oxide containing resins of the invention, and shows acomparison of the stability of the converted and the unconverted resins.

TABLE II Uneonverted resin, Percent percent Resin-Example number PerfectBroken Perfect Broken TABLE I Percent conver- Weak Strong Anion Molession to base base exchange Ex. starting Moles Time amine capacitycapacity capacity Percent No. resin H202 (hrs.) oxide meg/g meg./g meg/gsolids 0m 02 liberated.

EXAMPLE 4 The above data demonstrates the great increase in 150 g.(33.5% solids; 0.5 mole) of an epichlorohydrin- 5 stability for thoseresins which contain tertiary amine oxide functionality.

EXAMPLE 6 Deacidification of Glyoxal In order to evaluate the amineoxide containing resins as ion exchange resins and to confirm thephysical stability of such resins in an actual use application, amicrocycling technique was used by which a tertiary amine containingresin and a similar resin containing tertiary amine oxide groups wereexposed to sorptions and destarch solution. Essentially no oxygen wascollected in sorptions of weak and strong acids in a sequence similar tothat in field operation of deacidification of glyoxal. The compositionof the industrial glyoxal solution under consideration for treatment byion exchange means is as follows: (1) Aqueous solution of glyoxal, (2)0.75% HNO (3) 0.75% acetic acid, (4) unknown quantity of a colored acidwhich apparently is indigenous to the glyoxal. It is apparent that inthe operation of a weakly basic resin upon this acid mixture, the weakacids will form at least one distinct exhaustion band which will precedethe nitric acid exhaustion band. In essence, the phase sequence throughthe resin will be as follows: (1) Weak acids with the weaker onespreceding the stronger ones, (2) displacement of the weak acids bynitric acid, (2) regeneration of all the functionality to the freeamine.

To stimulate this sequence using a micro-cycler, a three phase systemwas set up as follows: (1) 2.25% acetic acid in an aqueous solution of15% glyoxal, (2) 2.25% HNO in an aqueous solution of 15% glyoxal, (3) 1N ammonia. The total cycle time is 1 hour. The higher concentrations ofacids were used in order to ensure complete conversion of the resins inthe micro-cycle.

The resins which were evaluated by this technique were (A) amacroreticular, weak base anion exchange resin containing tertiary aminefunctionality on a styrenedivinyl-benzene matrix and (B) a resin inwhich about of the tertiary amine groups in resin A were converted toamine oxide groups. After 155 microcycles, beads of the 'two resins wereexamined for physical deterioration. Among the beads of resin A, onlyabout 66% remained undamaged, while among the beads of resin B, about97% remained undamaged, thus confirming the physical stability of theamine oxide group containing resins in an actual ion exchangeapplication. This test also showed that resin B was effective inseparating the acids from the glyoxal mixture.

EXAMPLE 7 Adsorption of Phenol From Hexane In order to demonstrate theusefulness of the amine oxide containing resins of the invention for theadsorption of phenol from hexane, equilibrium experiments were performedusing a solution of 2.71 millimoles/liter of phenol in hexane and tworesinsa resin prepared in accordance with Example 1 with 100% conversionto amine oxide form and the same resin in its unconverted form. Fiftymilliliters of the phenol solution were equilibrated with a weighedquantity of resin for at least a week. After equilibration, the opticaldensities of the samples were measured at a wave length of 271 nm. on aBeckman-DU. The results obtained using each of the resins are summarizedin Table III.

TAB LE III Phenol adsorbed Equilibrium (mmole/gd concentration 10(nunolc/L) Uneonverted resin 7 Amine. oxide containing resin The abovedata demonstrates the eifectiveness and advantageousness over thecorresponding unconverted resins of the amine oxide containing resins inadsorbing phenol from hexane.

EXAMPLE 8 Adsorption of Octyl Alcotol From Benzene 12 tions weredetermined using gas chromatography. The results obtained using each ofthe resins are summarized in Table IV.

The above data demonstrates the effectiveness and advantageousness overthe corresponding unconverted resins of the amine oxide containingresins in adsorbing octyl alcohol from benzene.

EXAMPLE 9 Adsorption of Phenol From Benzene In order to demonstrate theusefulness of the amine oxide containing resins of the invention for theadsorption of phenol from benzene, column experiments were performedusing as a loading solution 500 ppm. of phenol in benzene and the sametwo resins evaluated in Example 7. The volume of adsorbent used was 10ml. (swollen in benzene) for each column. A flow rate of 0.5 gal./ft.min. (4 BV/hr.) was maintained throughout the experiments. Theanalytical method used was spectrophotometric determination usingbenzene as reference at a wave length of 278 run. The amine oxidecontaining resin had a capacity of 28 bed volumes to 0.5% leakage ascompared to 18 bed volumes for the unconverted resin. Excellentregeneration was obtained using 0.5% sodium hydroxide in methanol.

The above tests demonstrate the effectiveness and advantageousness overthe corresponding unconverted resins of the amine oxide containingresins in adsorbing phenol from benzene.

EXAMPLE 10 Deacidification of Formaldehyde To evaluate the amine oxidecontaining resins in the deacidification of formaldehyde, cyclingstudies were performed using a aqueous solution of formaldehydecontaining 0.5% formic acid. The tests were run at 160 F, the normaltemperature employed in the fields for this operation. I

The resins which were evaluated were (A) a macroreticular weak baseanion exchange resin containin tertiary amine functionality on astyrene-divinylbenzene matrix and (B) a resin in which about 25% of thetertiary amine group in resin A were converted to amine oxide groups.After 11 cycles beads of the two resins were EXAMPLE ll Ion ExchangeTreatment of Water Containing High Total Dissolved Solids vilatercontaining high concentrations of dissolved inorganic solids often causephysical breakdown when a bed containing weak base resins is used fordeionization following a cation exchange bed. To evaluate amine oxidecontaining resins in this application, a microcycling study was runalternating between exhaustion with a 0.25 N acid solution, consistingof approximately equal parts of hydrochloric acid and sulfuric acid, andregeneration with 1 N sodium hydroxide. After 500 cycles astyrene-divinylbenzene resin with about 25% of the tertiary amine groupsin the amine oxide form had over 99% perfect beads. This physicalstability is exceptionally good for a weak base ion exchange resin usedfor this application.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

I claim:

1. A process for removing acidic compounds from an aqueous solution ofan aldehyde selected from the group consisting of formaldehyde andglyoxal, which comprises contacting said solution with a resin havingweak base anion exchange properties, said resin being a crosslinked ionexchange or adsorbent polymeric resin matrix having a plurality offunctional groups selected from aliphatic or nonheterocyclic aromatictertiary amine oxide groups and aliphatic or non-heterocyclic aromatictertiary amine groups, wherein at least about to 100% of said functionalgroups are tertiary amine oxide groups, said tertiary amine oxide groupshaving the formula matrix-NR' wherein R and R are the same or dilferentalkyl, aryl, alkaryl, or aralkyl groups, or wherein R and R can be takentogether to form a saturated heterocyclic ring with the attachednitrogen atom, or wherein R and R can be joined with an R or R inanother tertiary amine oxide or tertiary amine group through an alkyleneor alkyleneamino chain, and wherein said tertiary amine groups have theformula /R matrix-N wherein R and R are as defined above.

2. A process according to claim 1 wherein the aldehyde is glyoxal.

References Cited UNITED STATES PATENTS 3,270,062 8/1966 Merz et al260-601 R 2,169,976 8/1939 Guenther et al. 260583 D FOREIGN PATENTS1,346,194 11/1963 France 260601 OTHER REFERENCES US. Cl. X.R. 260606

1. A PROCESS FOR REMOVING ACIDIC COMPOUNDS FROM AN AQUEOUS SOLUTION OF AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE AND GLYOXAL, WHICH COMPRISES CONTACTING SAID SOLUTION WITH A RESIN HAVING WEAK BASE ANION EXCHANGE PROPERTIES, SAID RESIN BEING A CRSOSLINKED ION EXCHANGE OR ADSORBENT POLYMERIC RESIN MATRIX HAVING A PLURALITY OF FUNCTIONAL GROUPS SELECTED FROM THE ALIPHATIC OR NONHETEROCYCLIC AROMATIC TERTIARY AMINE OXIDE GROUPS AND ALIPHTIC OR NON-HETEROCYCLIC AROMATIC TERTIARY AMINE GROUPS, WHEREIN AT LEAST ABOUT 5% TO 100% OF SAID FUNCTIONAL GROUPS ARE TERTIATY AMINE OXIDE GROUPS, SAID TERTIARY AMINE OXIDE GROUPS HAVING THE FORMULA 